An organic electroluminescence device is expected to be put into practical use as a next-generation display device because of its advantages over a liquid crystal display such as (1) a low power consumption, (2) a good view angle, (3) potential for becoming additionally thin, and (4) potential for enabling the utilization of a flexible substrate.
However, the organic electroluminescence device still involves a large number of problems to be solved before the device is put into practical use. Examples of the problems include low light emitting property, a short lifetime, and the difficulty of a process for turning the device into a thin film having a thickness at a level of several tens of nanometers. In particular, an improvement in property with which charge is injected from an electrode into an organic compound layer is indispensable for alleviating the low light emitting property and the short lifetime.
Doping the organic compound layer with, for example, an alkali metal, or an oxide, peroxide, or salt of the alkali metal is known to alleviate the low light emitting property and the short lifetime (Japanese Patent No. 3529543, Japanese Patent Application Laid-Open No. H10-270172, and Japanese Patent Application Laid-Open No. 2004-192842). In addition, with regard to a cesium suboxide, various compounds have been known (Coordination Chemistry Reviews, 163 (1997), 253-270).
Although the low light emitting property has been alleviated to some extent by an improvement in charge injecting property, the problem concerning the lifetime is not sufficiently solved yet.